Machine tool

ABSTRACT

A machine tool includes a bed including a bottom surface and legs arranged at three positions of the bottom surface. The bed includes two oblique sides arranged such that the bottom surface has a triangular shape. The machine tool also includes a first support surface arranged on the bed and extending along a substantially horizontal first axis, a work table supported by the first support surface so as to move along the first axis, a second support surface arranged on the bed and extending along a substantially horizontal second axis, which is perpendicular to the first axis, and a machining unit supported by the second support surface so as to move along the second axis. The second support surface is located higher than the first support surface.

CROSS REFERENCE TO RELATED APPLICATIONS

This Application claims priority to Japanese Patent Application SerialNo. 2018-105205, filed on May 31, 2018, and titled “VEHICLE”, andJapanese Patent Application Serial No. 2018-180738, filed on Sep. 26,2018 and titled “SYSTEM AND CONTROL METHOD,” which are incorporatedherein by reference in their entireties.

FIELD OF THE INVENTION

The following description relates to a machine tool.

BACKGROUND OF THE INVENTION

In typical machine tools, a bed is generally supported on aninstallation surface such as a floor surface at four positionscorresponding to the four corners of the bed. This support is generallyreferred to as four-point support. In such a four-point support, it isdifficult to perform height adjustment at the four points such that thebed is supported on the installation surface with a uniform force atevery point.

To cope with this problem, Japanese Laid-Open Patent Publication No.2005-131768 discloses a machine tool in which the bed is supported on aninstallation surface such as a floor surface at three points. In thismachine tool, support points on the installation surface are provided atthree positions of the lower surface of the bed, which has a simplequadrilateral box shape.

Japanese Laid-Open Patent Publication No. 10-138132 discloses a typicalgrinding machine in which a work table is supported on the bed such thatthe work table is movable back and forth in a sideward direction and acolumn is supported on the bed such that the column is movable back andforth in a front-rear direction in the same manner. A tool shaftincluding a tool is supported by the column such that the tool shaft ismovable up and down. Such a grinding machine is generally referred to ascolumnar type.

Conventionally, in some grinding machines, a saddle that moves back andforth in the front-rear direction is supported on the bed, and a worktable is supported on the saddle such that the work table is movableback and forth in the sideward direction. Further, a column is arrangedat a fixed position, and a tool shaft including a tool is supported onthe column such that the tool shaft is movable back and forth. Such agrinding machine is generally referred to as a saddle type.

In the machine tool of Japanese Laid-Open Patent Publication No.2005-131768, while three-point support is employed, the bed has a simplequadrilateral box shape. In order to ensure sufficient strength andstability, the bed needs to be formed through casting. Thus, it isdifficult to prevent the bed from becoming heavy. In addition, therigidity of the entire bed decreases. Decreases in the rigidity resultin decreases in the accuracy of machining a workpiece. Further, thequadrilateral box-shaped bed tends to be unstable when supported atthree points. Additionally, the bed has a high volume and weight. Thisreduces the natural frequency and thus reduces the resonant frequency,which adversely affects the machining accuracy. When the resonantfrequency of the bed decreases, the amplitude of vibration increases. Asa result, the machining accuracy decreases.

In the column-type grinding machine of Japanese Laid-Open PatentPublication No. 10-138132, when the column accelerates or decelerates inthe front-rear direction, the column tends to be inclined in thefront-rear direction due to the inertial force of the column. Further,in the column-type grinding machine, the column has a vertically longshape in which the column is relatively long in the vertical direction.This reduces the thickness of the bed located below the column. That is,since the vertically-long, heavy column moves in the front-reardirection on the thin bed, the bed easily deforms due to the weight ofthe column. Thus, it is difficult to limit decreases in the positionaccuracy of the column in the vertical direction. As a result, machiningwith high accuracy is difficult.

In the saddle-type grinding machine, the table is mounted on the saddlethat moves back and forth. Thus, the total weight of the saddle and thetable may be excessive. While the saddle needs to be reduced in size inorder to decrease the weight, the table needs to have a certain lengthin the sideward direction for machining a workpiece. Thus, the oppositeends of the table protrude from the saddle and are overhung.Accordingly, when the table that moves in the sideward directionparticularly reaches the right or left movable end, the overhung partdroops greatly. As a result, machining with high accuracy is difficult.

SUMMARY OF THE INVENTION

This Summary is provided to introduce a selection of concepts in asimplified form that are further described below in the DetailedDescription. This Summary is not intended to identify key features oressential features of the claimed subject matter, nor is it intended tobe used as an aid in determining the scope of the claimed subjectmatter.

It is an objective of the following description to provide a machinetool in which the accuracy of machining a workpiece is improved.

According to one general aspect, a machine tool includes a bed includinga bottom surface and legs arranged at three positions of the bottomsurface. The bed includes two oblique sides arranged such that thebottom surface has a triangular shape.

According to another general aspect, a machine tool includes a bed, afirst support surface arranged on the bed, the first support surfaceextending along a substantially horizontal first axis, a work tablesupported by the first support surface such that the work table movesback and forth along the first axis, a second support surface arrangedon the bed, the second support surface extending along a substantiallyhorizontal second axis, which is perpendicular to the first axis, amachining unit supported by the second support surface such that themachining unit moves back and forth along the second axis, a thirdsupport surface arranged at the machining unit, the third supportsurface extending along a substantially vertical third axis, and amachining shaft unit supported by the third support surface such thatthe machining shaft unit moves in a vertical direction along the thirdaxis, the machining shaft unit including a tool for machining aworkpiece on the work table. The second support surface is located at aposition higher than the first support surface.

Other features and aspects will be apparent from the following detaileddescription, the drawings, and the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a machine tool according to a firstembodiment as viewed from above.

FIG. 2 is an exploded perspective view of the machine tool shown in FIG.1 .

FIG. 3 is a perspective view of the machine tool of FIG. 1 as viewedfrom below.

FIG. 4 is a front view of the machine tool shown in FIG. 1 .

FIG. 5 is a partially broken front view of the machine tool shown inFIG. 4 .

FIG. 6 is a side view of the machine tool shown in FIG. 1 .

FIG. 7 is a cross-sectional view taken along line 7-7 in FIG. 4 .

FIG. 8 is a cross-sectional view taken along line 8-8 in FIG. 6 .

FIG. 9 is a partial cross-sectional view of a machine tool according toa second embodiment.

FIG. 10 is a partial cross-sectional view of the machine tool shown inFIG. 9 .

Throughout the drawings and the detailed description, the same referencenumerals refer to the same elements. The drawings may not be to scale,and the relative size, proportions, and depiction of elements in thedrawings may be exaggerated for clarity, illustration, and convenience.

DETAILED DESCRIPTION

This description provides a comprehensive understanding of the methods,apparatuses, and/or systems described. Modifications and equivalents ofthe methods, apparatuses, and/or systems described are apparent to oneof ordinary skill in the art. Sequences of operations are exemplary, andmay be changed as apparent to one of ordinary skill in the art, with theexception of operations necessarily occurring in a certain order.Descriptions of functions and constructions that are well known to oneof ordinary skill in the art may be omitted.

Exemplary embodiments may have different forms, and are not limited tothe examples described. However, the examples described are thorough andcomplete, and convey the full scope of the disclosure to one of ordinaryskill in the art.

First Embodiment

A first embodiment of the present disclosure will now be described withreference to the drawings.

As shown in FIGS. 1 and 2 , a machine tool according to a firstembodiment includes a bed 10 and a table 12. The bed 10 includes a bedbody 11. The table 12 is supported to be movable along a horizontalX-axis at the front part of the bed body 11. The X-axis, which is afirst axis, extends in the sideward direction of the machine tool.Further, the machine tool includes two support members 14 and amachining unit 15. The two support members 14 are respectively fixed tothe opposite sides of the upper surface of the bed body 11. Themachining unit 15 is supported to be movable along a horizontal Z-axison the two support members 14. The Z-axis, which is a second axis,extends in the front-rear direction of the machine tool and isperpendicular to the X-axis. The support members 14 configure part ofthe bed 10. The machining unit 15 includes a rotation grindstone 16movable along a Y-axis. The Y-axis, which is a third axis, extends inthe vertical direction of the machine tool and is perpendicular to theX-axis and Z-axis. In a state in which a workpiece is supported on thetable 12, the table 12 moves along the X-axis and the rotationgrindstone 16 moves along the Z-axis and the Y-axis. With suchmovements, the rotation grindstone 16 rotates about an axis parallel tothe Z-axis is used to perform a predetermined machining on theworkpiece.

The structure of each component of the machine tool will now bedescribed in detail.

First, the bed body 11 and the components related to the bed body 11will be described.

Referring to FIGS. 1 to 3 , the bed body 11 is an integrated bodyentirely formed through casting and includes a substantially triangularbottom plate 20, two side plates, a front plate 23, and a rear plate 24.Each of the two side plates includes a substantially triangular lowerside plate 21 and a substantially triangular upper side plate 22. Thelower side plate 21 is one example of an oblique side. The upper edgesof the two side plates, that is, the upper edges of the two upper sideplates 22, extend along the Z-axis in parallel to each other. The upperends of the two upper side plates 22 are provided with horizontal upperplates 25, and the front surfaces of the two upper side plates 22 areprovided with upright plates 26. As shown in FIG. 7 , an inner plate 27is arranged rearward from the front plate 23. As shown in FIG. 2 , thebed body 11 includes an open portion 28 that opens upward between thetwo upper plates 25.

As shown in FIG. 3 , the bottom plate 20 is triangular because of thearrangement of the lower side plates 21, which are the oblique sides.That is, the lower side plates 21 are configured and arranged such thatthe bottom plate 20 has a triangular shape. In other words, the lowerside plates 21 are arranged to define the bottom plate 20 in atriangular shape. The lower edges of the two side plates, that is, thelower edges of the two lower side plates 21, configure two of the threeouter edges (sides) of the triangular bottom plate 20. Thus, the bottomplate 20 includes two triangular tops located at the front part of thebottom plate 20 and the remaining one triangular top located at the rearpart of the bottom plate 20. The three tops are provided with legs. Thatis, the two front tops are provided with front legs 31, and the rear topis provided with a rear leg 32. The two front legs 31 are located on aline parallel to the X-axis, and the rear leg 32 is located on a linethat extends through the center of the two front legs 31 and is parallelto the Z-axis.

As shown in FIGS. 6 and 7 , each front leg 31 includes a fixed cam body34 that has an inclined surface 33 and a leg member 35 that is movableup and down. The upper surface of the leg member 35 is provided with amovable cam body 37 having an inclined surface 36 that is in contactwith the inclined surface 33. The leg member 35 is prevented from beingseparated from the fixed cam body 34 and the bed body 11 by restrictionportions 39 arranged at the front and rear of the leg member 35. The legmember 35 is arranged on an installation surface such as a floorsurface. Screw action based on rotation of an adjustment screw 38 causesthe inclined surface 33 of the movable cam body 37 to slide on theinclined surface 36 of the fixed cam body 34. This moves the leg member35 up and down. As a result, the height of the front leg 31 is adjusted.The height of the rear leg 32 is fixed.

As shown in FIGS. 3, 6, and 7 , the rear plate 24 is inclined such thatthe lower part is located frontward from the upper part. A rear endcorner of the bottom plate 20 is located rearward from the rear plate24, and the rear leg 32 is located at the rear end corner. Tworeinforcement ribs 41, which are reinforcement portions, are providedbetween the rear end corner of the bottom plate 20 and the outer surfaceof the rear plate 24. The two reinforcement ribs 41 have a triangularshape. Further, the two reinforcement ribs 41 are inclined and extendedsuch that the reinforcement ribs 41 are located closer to each othertoward the lower side. The reinforcement ribs 41 are integrated with therear end corner of the bottom plate 20 and the rear plate 24. Rear ends29 of the two lower side plates 21 extend to the lower ends of thereinforcement ribs 41.

As shown in FIGS. 1, 2, and 6 , a gutter-shaped table traveling portion43 extending along the X-axis is arranged between the front ends of thetwo upper side plates 22 at the front of the upright plates 26. Thetable traveling portion 43 opens upward and has opposite ends that openin the longitudinal direction. The two front legs 31 are locatedimmediately below the opposite ends of the table traveling portion 43,more specifically, located immediately below the center of the oppositeends in the width direction. The opposite ends of the table travelingportion 43 are closed by end members 44. First guide rails 45 are fixedto the table traveling portion 43 between the two end members 44 suchthat the first guide rails 45 are arranged back and forth. The firstguide rails 45 are first support surfaces. The table 12 is supported bythe first guide rails 45 to be slidable along the X-axis. The table 12is moved along the X-axis by, for example, a linear motor (not shown).

As shown in FIGS. 1, 2, 4, and 5 , the two support members 14 arerespectively fixed on the upper surfaces of the two upper plates 25 bybolts 13 such that the support members 14 are located on the oppositesides of the open portion 28. The upper parts of the front ends of thetwo support members 14 are provided with overhung parts 51 that protrudefrontward. A second guide rail 52 extending along the Z-axis is coupledto the upper surface of each support member 14. The second guide rail52, which is a second support surface, extends over the entire length ofthe support member 14 including the overhung part 51 in the direction inwhich the Z-axis extends.

As shown in FIGS. 1 and 2 , a unit frame 61, which is a support body,arranged between the second guide rails 52 and in the open portion 28.The unit frame 61 is movable along the Z-axis. The unit frame 61includes two sliders 62, which are side members, and quadrilateralsupport frame 63. The two sliders 62 are respectively supported by thetwo second guide rails 52. The support frame 63 is arranged between thetwo sliders 62 and fixed to the two slides 62. Third guide rails 65extending along the Y-axis are coupled to the inner surface of thesupport frame 63. The third guide rails 65 are third support surfaces.When linear motors 66 arranged on the opposite sides of the supportframe 63 are driven, the support frame 63 and the sliders 62 move backand forth along the second guide rails 52 in the open portion 28. Acurved portion, that is, a side bulged portion 67 bulged outward in anarcuate manner, is integrated with the outer surface of each slider 62.Reinforcement ribs 68 are integrated with the inner surface of thesupport frame 63. Curved portions, that is, rear bulged portions 69bulged in an arcuate manner, are integrated with the rear surface ofeach support frame 63.

As shown in FIGS. 1, 2, and 7 , a lift frame 71 is supported by thethird guide rails 65 to be movable up and down in the support frame 63.A motor 72 is coupled to the lower end of the support frame 63. In thesupport frame 63, a ball screw 73 is supported to extend along theY-axis. The ball screw 73 rotates when the motor 72 is driven. The liftframe 71 moves up and down as the ball screw 73 rotates forward andbackward. A grindstone shaft unit 74, which is a machining shaft unit,is supported by the lift frame 71. A grindstone shaft 76 that is rotatedby a motor 75 is supported by the grindstone shaft unit 74. The rotationgrindstone 16, which is located frontward from the overhung parts 51, issupported by the front end of the grindstone shaft 76.

In the present embodiment, the machining unit 15 is configured by, forexample, the unit frame 61, the lift frame 71, and the grindstone shaftunit 74. As shown in FIG. 7 , in a state in which the machining unit 15is supported by the second guide rails 52, the center of gravity α ofthe machining unit 15 is located in the inner space of the bed body 11.The center of gravity α of the machining unit 15 is located at aposition lower than the second guide rails 52. Further, the center ofgravity β of the machine tool is located at a position lower than thecenter of gravity α of the machining unit 15.

As shown in FIGS. 3, 4, and 8 , the lower surface of the bed body 11 hasan arcuate recess 81. The recess 81 is located immediately below thecenter of the table traveling portion 43 in the longitudinal directionand the width direction. In the recess 81, two projections 82 are spacedapart from each other. Receiving members 83 are respectively fixed tothe lower surfaces of the two projections 82. The receiving members 83respectively include internal threads 84 in which the spirals are woundin different directions. Threaded parts of the opposite ends of anexternal thread member 85 are coupled to the two internal threads 84.The receiving members 83, which are first thread bodies, and theexternal thread member 85, which is a second thread body, configure anadjustment member 86 having the form of a turnbuckle. A locknut 87 thatresists loosening is coupled to each threaded part of the externalthread member 85. The locknut 87 is configured by, for example, a doublenut. An operation part arranged on the center of the external threadmember 85 is operated to rotate the external thread member 85. Thiscauses the two receiving members 83 to receive force that moves thereceiving members 83 toward or away from each other. As a result, thebed body 11 is deformed to adjust the straightness of the first guiderail 45.

The two upper side plates 22, the front plate 23, the rear plate 24, theinner plate 27, and the table traveling portion 43 have through-holes91, which are thinned portions. The through-holes 91 have various shapessuch as quadrilateral, circle, triangle, trapezoid, and deformedquadrilateral. The lower surface of the bottom plate 20 has recesses 90.

As shown in FIGS. 7 and 8 , two plate-shaped first reinforcement frames92 and two plate-shaped second reinforcement frames 93 are arrangedbetween the front plate 23 and the inner plate 27. The firstreinforcement frames 92 and the second reinforcement frames 93, whichare reinforcement portions, are integrated with the front plate 23 andthe inner plate 27. As shown in FIG. 8 , as viewed in the direction inwhich the Z-axis extends, the first reinforcement frames 92 and thesecond reinforcement frames 93 are symmetrical. The first reinforcementframes 92 and the second reinforcement frames 93 cross each other to beintegrated with each other. Quadrilateral through-holes 91, which arethinned portions, extend through the middle parts of the firstreinforcement frames 92 and the second reinforcement frames 93 in thevertical direction. The first reinforcement frames 92 extend from thecenter of the lower surface of the table traveling portion 43 to theintersection parts of the upper side plate 22 and the bottom plate 20.Thus, the front legs 31 and the surroundings of the front legs 31 arereinforced by the intersection points. The second reinforcement frames93 extend from the center of the lower surface of the table travelingportion 43 to the part of the bottom plate 20 where the recess 81 islocated. The front plate 23 and the inner plate 27 have through-holes 91at positions located away from the first reinforcement frames 92 and thesecond reinforcement frames 93.

The operation of the machine tool will now be described.

In the machine tool of the present embodiment, a workpiece is supportedon the table 12. In a state in which the rotation grindstone 16 isrotating, the lift frame 71 and the rotation grindstone 16 are movedalong the third guide rails 65 in the direction in which the Y-axisextends. This adjusts the height of the rotation grindstone 16. Further,the table 12 is moved back and forth along the first guide rails 45 inthe direction in which the X-axis extends, and the grindstone shaft unit74 and the rotation grindstone 16 are moved along the second guide rails52 in the direction in which the Z-axis extends. In this manner, therotation grindstone 16 is used to grind the workpiece.

The machine tool of the present embodiment has the following advantages.

(1) The machine tool includes two front legs 31 and one rear leg 32 atthree positions of the bottom surface of the bottom plate 20 of the bed10. Thus, the machine tool is supported at three points on aninstallation surface such as the floor surface of a factory. That is,the machine tool can be supported stably regardless of the flatness ofthe installation surface. As the adjustment screws 38 of the front legs31 are operated, the inclined surfaces 33 and 36 slide relative to eachother. This adjusts the heights of the leg members 35 of the front legs31. Thus, the horizontality and height of the machine tool aremaintained properly. In contrast, in a bed with four-point support,adjusting the heights of the legs is troublesome. Thus, the accuracy ofmachining a workpiece may be reduced due to insufficient adjustment.Three-point support allows adjustment to be performed relatively easilyand thus reduces such inconvenience.

(2) The bottom plate 20 of the bed body 11 has a triangular shape. Thus,as compared to a prior-art machine tool having a quadrilateral bottomplate, the bed body 11 is reduced in size. This reduces the weight ofthe machine tool. Particularly, in the present embodiment, the bottomplate 20 is substantially triangular, and the lower side plate 21 andthe upper side plate 22 are triangular. Further, the rear plate 24 isinclined such that the lower part is located frontward from the upperpart. This reduces the volume of the bed body 11 and thus furtherreduces the size and weight of the bed body 11. Such reduction of thebed body 11 in size improves the rigidity of the entire bed body 11 andincreases the accuracy of machining a workpiece. Additionally, the bedbody 11 includes the recesses 90 and the through-holes 91 at multiplepositions of the bed body 11 while satisfying the required strength.This reduces limits on installation places of the machine tool andfacilitates movement and conveyance of the machine tool.

(3) The reduction of the bed body 11 in size, the reduction of thevolume of the bed body 11, and the formation of the recesses 90 and thethrough-holes 91 allow the bed body 11 to be formed with fewercomponents and reduced in weight. This increases the natural frequencyof the bed body 11. When the vibration energy is the same, the amplitudeof the resonant frequency decreases as the resonant frequency of the bedbody 11 increases. Thus, the machining accuracy is improved.

(4) The parts of the bed body 11 other than the table traveling portion43 have a smaller width than the table traveling portion 43 (dimensionalong the X-axis). Further, the bed body 11 includes the lower sideplates 21, which are triangular, and thus gradually decreases in widthtoward the rear. Thus, as described above, the bed body 11 can bereduced in size and weight. This allows for machining with highaccuracy. Additionally, space exists below each of the lower side plates21 of the bed body 11. This space can be employed to install hydraulicpipes and wires.

(5) The front legs 31 are arranged at the positions corresponding to theopposite ends of the table traveling portion 43. Thus, even if the partof the bed body 11 located rearward from the table traveling portion 43has a smaller width than the table traveling portion 43, the tabletraveling portion 43 is prevented from being deformed. This allows formachining with high accuracy.

(6) The first and second reinforcement frames 92 and 93, which areintegrated with the table traveling portion 43 and are inclined toextend such that the first and second reinforcement frames 92 and 93cross each other, are arranged below the table traveling portion 43.This prevents the table traveling portion 43 from deforming and thusallows for machining with high accuracy. Further, the first and secondreinforcement frames 92 and 93 are inclined to extend, and the lowerends of the first reinforcement frames 92 are integrated with the upperside plates 22, where the front legs 31 are located. In addition, thetwo second reinforcement frames 93 converge at the lower center of thebed body 11 to be integrated with each other. Thus, machining pressureacting on the table traveling portion 43 is applied to the first andsecond reinforcement frames 92 and 93 in a direction in which the firstand second reinforcement frames 92 and 93 are compressed. Thiseffectively prevents deformation of the table traveling portion 43.

(7) The rear leg 32 is located rearward from the table traveling portion43 on a line that extends through the center of the table travelingportion 43 in the longitudinal direction and is parallel to the Z-axis.Thus, since the rear leg 32 is located immediately below the movablerange of the unit frame 61, which includes the grindstone shaft unit 74,the unit frame 61 moves stably. This contributes to the high-accuracymachining of a workpiece.

(8) The sliders 62 of the unit frame 61, which are supported by thesecond guide rails 52, are provided with the side bulged portions 67,which bulge in the horizontal direction. This improves the rigidity forsupporting the unit frame 61 and contributes to the high-accuracymachining of a workpiece.

(9) The reinforcement ribs 68 are formed on the inner side of thesupport frame 63 of the unit frame 61. Further, the rear bulged portions69, which bulge rearward, are arranged at the rear part of the supportframe 63. This improves the rigidity for supporting the unit frame 61and contributes to the high-accuracy machining of a workpiece.

(10) The unit frame 61 is supported by the second guide rails 52 via thesliders 62, which are located on the opposite sides of the unit frame61. Further, the machining unit 15 is located in the inner space of thebed body 11 through the open portion 28 of the bed body 11. This allowsthe machining unit 15, which is the uppermost part of the machining unit15, to be located at a lower position and thus lowers the height of theentire machining unit 15. Further, the motor 72, which drives the ballscrew 73 of the machining unit 15, is located at the lower part of themachining unit 15. This also allows the center of gravity α of themachining unit 15 to be located below the second guide rail 52. In thismanner, the center of gravity α can be located at a low position in thebed body 11. This lowers the height of the machining unit. Thus, themachining unit 15 can be supported stably. Further, vibration of themachining unit 15 is limited to improve the accuracy of machining aworkpiece.

(11) Since the center of gravity β of the machine tool is located at aposition lower than the center of gravity α of the machining unit 15,the machining unit 15 can be installed stably. This reduces vibration ofthe machine tool and improves the accuracy of machining a workpiece.

(12) The front ends of the two support members 14 are provided with theoverhung parts 51, which protrude frontward. Thus, even if thegrindstone shaft unit 74 is moved forward to machine a workpiece, thegrindstone shaft 76 is rarely cantilevered. Accordingly, even if thegrindstone shaft 76 is moved forward to a large extent, decreases in theaccuracy of machining a workpiece are limited.

(13) The front plate 23 of the bed body 11 is inclined such that thelower part is located rearward from the upper part. This limitsinterference of the front plate 23 with the lower limbs of a worker suchas a toe located on the front side of the bed body 11. Thus, the workercan perform operations easily.

(14) The framework of the machine tool is configured as an assembledunit including multiple members such as the bed body 11, the supportmembers 14, the support frame 63, the sliders 62, and the unit frame 61.Further, the movement accuracy of the members that move along theX-axis, the Y-axis, and the Z-axis can be easily adjusted by adjustingthe positional relationship of the members that configure the frameworkof the machine tool.

(15) The reinforcement ribs 41 are arranged above the rear leg 32. Thus,even if the rear plate 24 is inclined, the strength and rigidity of theportion where the rear leg 32 is located are ensured.

(16) The adjustment member 86, which has the form of a turnbuckle, islocated at the lower center of the front end of the bed body 11. Thecurvedness of the bed body 11 (especially, the lower front part of thebed body 11) can be adjusted by loosening the locknuts 87 and rotatingthe adjustment member 86. Thus, the adjustment member 86 facilitatesfine adjustment of the degree of deformation and the inclination anglerelative to the horizontal surface of the table traveling portion 43.This improves the movement accuracy of the table 12 and consequentlyimproves the accuracy of machining a workpiece.

(17) The through-holes 91 are formed at multiple positions of the bedbody 11. Thus, air flows smoothly between the inside and outside of themachine tool through the through-holes 91. This limits differences inthe temperature of the inside and outside of the machine tool, limitsthe deformation of the machine tool resulting from the temperature, andimproves the accuracy of machining a workpiece. Additionally, the innerpart of the machine tool can be checked, inspected, and cleaned throughthe through-holes 91. This improves the maintainability of the machinetool.

(18) The second guide rails 52, which are the second support surfacesthat guide movement of the machining unit 15 including the grindstoneshaft unit 74 and the support frame 63 along the Z-axis of the machiningunit 15, are located at a position higher than the first guide rails 45,which are the first support surfaces. This increases the dimension(height or thickness) of the portion of the bed 10 in the verticaldirection located below the second guide rails 52. Accordingly, therigidity of the portion that supports the second guide rail 52 isimproved to limit the deformation of the bed 10 resulting from load onthe machining unit 15. This improves the movement accuracy of themachining unit 15 and the machining accuracy.

(19) As described above, the second guide rails 52 are located at aposition higher than the first guide rails 45. This eliminates the needto arrange a tall, heavy column that supports the grindstone shaft unit74. This avoids inconveniences such as inclination of the column thatresults from acceleration and deceleration of the column. This allowsthe machining unit 15 to be accurately moved straight along the secondguide rails 52, ensures the position accuracy of the grindstone shaftunit 74, and allows for high-accuracy machining as described above.

Second Embodiment

A second embodiment of the present disclosure will now be described,mainly focusing on the differences from the first embodiment.

As shown in FIGS. 9 and 10 , in the second embodiment, the adjustmentmember 86 of the first embodiment, which has the form of a turnbuckle,is replaced with an adjustment member 186 as described below. That is,the recess 81 located at the lower center of the bed body 11 has twoinner surfaces opposed to each other, and fixed wedge members 95including inclined surfaces 96 are respectively fixed to the innersurfaces. An adjustment screw 97 is supported by the bed body 11 suchthat the adjustment screw 97 cannot move in the axial direction andcannot rotate. An internal thread 100 of a movable wedge member 99 iscoupled with the adjustment screw 97. The opposite side surfaces of themovable wedge member 99 have inclined surfaces 98. The inclined surfaces98 are respectively in close contact with the inclined surfaces 96 ofthe fixed wedge members 95.

When the adjustment screw 97 is rotated, the movable wedge member 99moves along the Z-axis in a first direction or in a second direction,which is opposite to the first direction. As the movable wedge member 99moves, the two fixed wedge members 95 move toward or away from eachother. This adjusts the flexing amount of the bed body 11 and adjuststhe straightness of the first guide rails 45.

Modifications

The first and second embodiments may be modified as described below.

The locations of the adjustment members 86 and 186 may be changed to,for example, the rear part of the bed body 11.

The number of the adjustment members 86 and 186 may be changed. Forexample, the adjustment members 86 and 186 may be arranged at the lowerrear part of the bed body 11 and/or the opposite sides of the rear partof the bed body 11 in addition to the center of the lower front part ofthe bed body 11. Alternatively, the adjustment members 86 and 186 may bearranged at the middle and/or upper part of the bed body 11 in thevertical direction in addition to the lower part of the bed body 11.

The tool is not limited to a rotation grindstone and may be, forexample, a drill, a milling cutter, an endmill, or a hob.

The recesses 90 or the through-holes 91, which are the thinned portions,may be omitted.

The lower side plates 21, which are the oblique sides, may be omitted.The upper side plate 22 may be inclined in the same manner as the lowerside plates 21 such that at least part of the upper side plate 22configures the oblique sides.

The bed body 11 and the support members 14 may be formed as anintegrated body.

The adjustment member that adjusts the deformation amount of the bedbody 11 may include two external thread bodies (first thread bodies)fixed to the bed body 11 and arranged coaxially to be opposed to eachother and an internal thread body (second thread body) arranged betweenthe two external thread bodies and coupled to the two external threadbodies. The internal thread body includes an operation part and threadedparts that respectively extend from the opposite ends of the operationpart. When the internal thread body is rotated, the two external threadbodies move toward or away from each other, thereby adjusting thedeformation amount of the bed body 11.

The technical ideas understood from the above-described embodiments andthe modifications are as follows.

(A) A machine tool comprising:

-   -   a bed;    -   a table traveling portion arranged at an upper front part of the        bed;    -   a work table configured to travel along the table traveling        portion; and    -   legs arranged at three positions of a bottom surface of the bed,        wherein    -   the legs include two front legs arranged at positions        corresponding to opposite ends of the table traveling portion in        a longitudinal direction, and    -   the table traveling portion has a length larger than a width of        a part of the bed located rearward from the table traveling        portion.

(B) The machine tool according to item (A), wherein the legs includes arear leg arranged rearward from a center of the table traveling portionin the longitudinal direction.

(C) A machine tool comprising:

-   -   a bed; and    -   an adjustment member configured to adjust a deformation degree        of the bed, the adjustment member being arranged at the bed,    -   wherein the adjustment member includes    -   two first thread bodies fixed to the bed, the two first thread        bodies being arranged coaxially to be opposed to each other, and    -   a second thread body including an operation part and two        threaded parts respectively arranged at opposite ends of the        operation part and coupled to the first thread bodies.

The adjustment member of the machine tool according to item (C) is alsoapplicable to a machine tool other than the above-described embodiments,for example, a machine tool including four legs and supported at fourpoints on an installation surface.

(D) A machine tool comprising:

-   -   a bed; and    -   an adjustment member configured to adjust a deformation degree        of the bed, the adjustment member being arranged at the bed,    -   wherein the adjustment member includes    -   two fixed wedge members fixed to the bed and opposed to each        other, and    -   a movable wedge member arranged between the fixed wedge members        and engaged with the fixed wedge members.

The adjustment member of the machine tool according to item (D) is alsoapplicable to a machine tool other than the above-described embodiments,for example, a machine tool including four legs and supported at fourpoints on an installation surface.

(E) The machine tool according to item (C) or (D), comprising a tabletraveling portion arranged at a front part of the bed and extendingalong a first axis,

-   -   wherein the adjustment member is located at a position        corresponding to a center of the table traveling portion in a        longitudinal direction.

(F) The machine tool according to any one of claims 1 to 11, wherein thebed includes a reinforcement portion configured to reinforce the legs.

(G) The machine tool according to claim 3, wherein

-   -   the bed includes a reinforcement portion arranged below the        table traveling portion, and    -   the two front legs are arranged at positions corresponding to        the reinforcement portion.

(H) The machine tool according to any one of claims 1 to 11, wherein thebed includes a bed body and two support members that support themachining unit, the two support members being respectively arranged onopposite sides of an upper surface of the bed body.

(I) The machine tool according to claim 15, comprising:

-   -   two front legs arranged at positions of a lower part of the bed        that correspond to opposite ends of the first support surface;        and    -   a rear leg arranged at one position of the lower part of the bed        located between the second support surfaces.

What is claimed is:
 1. A machine tool comprising: a bed, the bedincluding: a bottom surface having a triangular shape, the bottomsurface extending in a horizontal plane; two oblique plates, each havinga respective major plane extending obliquely with respect to a verticalplane and the horizontal plane; and two side plates, a first of the twoside plates being disposed above a first of the two oblique plates, anda second of the two side plates being disposed above a second of the twooblique plates; legs arranged at three positions of the bottom surface,wherein the first of the two oblique plates meets the bottom surface atthe horizontal plane so as to form a first outer edge of the triangularshape, and the second of the two oblique plates meets the bottom surfaceat the horizontal plane so as to form a second outer edge of thetriangular shape, the first of the two oblique plates extends from thefirst outer edge to the first of the two side plates and forms arespective oblique edge therewith, the respective oblique edge beingoblique with respect to the vertical and horizontal planes, the secondof the two oblique plates extends from the second outer edge to thesecond of the two side plates and forms a respective oblique edgetherewith, the respective oblique edge being oblique with respect to thevertical and horizontal planes.
 2. The machine tool according to claim1, wherein the two side plates include upper edges extending in parallelto each other.
 3. The machine tool according to claim 1, furthercomprising: a table traveling portion arranged at a front part of thebed and extending along a first axis; and a table configured to supporta workpiece, the table being supported by the table traveling portionsuch that the table moves along the first axis, wherein the legsinclude: two front legs arranged at positions corresponding to oppositeends of the table traveling portion, and one rear leg arranged rearwardfrom the table traveling portion, the rear leg being located on a linethat extends through a center of the table traveling portion in alongitudinal direction and is orthogonal to the first axis.
 4. Themachine tool according to claim 3, wherein a portion of the bed locatedrearward from the table traveling portion has a smaller width than alength of the table traveling portion in a direction extending along thefirst axis.
 5. The machine tool according to claim 3, furthercomprising: a support body supported by the bed at a position locatedrearward from the table traveling portion such that the support bodymoves along a second axis, which is orthogonal to the first axis; and amachining shaft unit supported by the support body, the machining shaftunit including a tool, wherein at least one of a side part or a rearpart of the support body is provided with a reinforcing curved portion.6. The machine tool according to claim 5, wherein a portion of the bedsupporting the support body includes an overhung part protruding towardthe table traveling portion.
 7. The machine tool according to claim 5,wherein the bed includes an open portion that opens upward, and thesupport body supports the machining shaft unit to be movable in avertical direction, the support body being arranged in an inner space ofthe bed through the open portion.
 8. The machine tool according to claim3, wherein the bed includes a front plate inclined such that a lowerpart of the front plate is located rearward from an upper part of thefront plate.
 9. The machine tool according to claim 3, furthercomprising an adjustment member arranged at a lower part of the bed,wherein the adjustment member includes: two first thread bodies fixed tothe bed, the two first thread bodies being arranged coaxially to beopposed to each other, and a second thread body including an operationpart and two threaded parts respectively arranged at opposite ends ofthe operation part and coupled to the first thread bodies.
 10. Themachine tool according to claim 9, wherein the adjustment member islocated below the center of the table traveling portion in thelongitudinal direction.
 11. The machine tool according to claim 1,further comprising: a first support surface arranged on the bed, thefirst support surface extending along a substantially horizontal firstaxis; a work table supported by the first support surface such that thework table moves back and forth along the first axis; a second supportsurface arranged on the bed, the second support surface extending alonga substantially horizontal second axis, which is perpendicular to thefirst axis; a machining unit supported by the second support surfacesuch that the machining unit moves back and forth along the second axis;a third support surface arranged at the machining unit, the thirdsupport surface extending along a substantially vertical third axis;wherein the machining unit includes a machining shaft unit which issupported by the third support surface such that the machining shaftunit moves in a vertical direction along the third axis, the machiningshaft unit including a tool for machining a workpiece on the work table,wherein the second support surface is located at a position higher thanthe first support surface.
 12. A machine tool, comprising: a bed; firstguide rails arranged on the bed, the first guide rails extending along asubstantially horizontal first axis; a work table supported by the firstguide rails such that the work table moves back and forth along thefirst axis; second guide rails arranged on the bed, the second guiderails extending along a substantially horizontal second axis, which isperpendicular to the first axis; a machining unit supported by thesecond guide rails such that the machining unit moves back and forthalong the second axis; third guide rails arranged at the machining unit,the third guide rails extending along a substantially vertical thirdaxis; wherein the machining unit includes a machining shaft unit whichis supported by the third guide rails such that the machining shaft unitmoves in a vertical direction along the third axis, the machining shaftunit including a tool for machining a workpiece on the work table,wherein the second guide rails are located at a position higher than thefirst guide rails, a center of gravity of the machine tool is located ata position lower than a center of gravity of the machining unit thereof,and the center of gravity of the machining unit is located at a positionlower than the second guide rails.
 13. The machine tool according toclaim 12, wherein the bed includes a bed body, and two support membersrespectively arranged on opposite sides of an upper surface of the bedbody, the support members each including a respective second guide railof the second guide rails.
 14. The machine tool according to claim 13,wherein the upper surface of the bed body is located at a positionhigher than the first guide rails.
 15. The machine tool according toclaim 12, wherein the second guide rails include two second guide rails,and the machining unit includes: two side members respectively supportedby the two second guide rails, and a support frame arranged between theside members and supported by the side members, the support frameincluding the third guide rails.
 16. The machine tool according to claim15, wherein an outer surface of each of the side members is providedwith a respective reinforcing curved portion.
 17. The machine toolaccording to claim 15, wherein the bed includes an open portion thatopens upward, and the support frame is arranged in an inner space of thebed through the open portion.
 18. The machine tool according to claim12, wherein a portion of the bed supporting the machining unit includesan overhung part protruding toward the first guide rails.
 19. Themachine tool according to claim 12, wherein a portion of the bed locatedrearward from the first guide rails has a smaller width than a length ofthe first guide rails in a direction extending along the first axis.